SARS‐CoV‐2 infection rate in Antananarivo frontline health care workers, Madagascar

Abstract Background Health care workers (HCWs) represent a vulnerable population during epidemic periods. Our cohort study aimed to estimate the risk of infection and associated factors among HCWs during the first wave of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) in Madagascar. Methods A prospective cohort study was carried out in three hospitals that oversaw the first cases of COVID‐19. Monthly ELISA‐based serological tests were conducted, and nasopharyngeal swabs were collected in the case of symptoms linked to COVID‐19 for RT–PCR analysis. Survival analyses were used to determine factors associated with SARS‐CoV‐2 infection. Results The study lasted 7 months from May 2020. We included 122 HCWs, 61.5% of whom were women. The median age was 31.9 years (IQR: 26.4–42.3). In total, 42 (34.4%) had SARS‐CoV‐2 infections, of which 20 were asymptomatic (47.6%). The incidence of SARS‐CoV‐2 infection was 9.3% (95% CI [6.5–13.2]) person‐months. Sixty‐five HCWs presented symptoms, of which 19 were positive by RT–PCR. When adjusted for exposure to deceased cases, infection was more frequent in HCWs younger than 30 years of age (RR = 4.9, 95% CI [1.4–17.2]). Conclusion Our results indicate a high incidence of infection with SARS‐CoV‐2 among HCWs, with a high proportion of asymptomatic cases. Young HCWs are more likely to be at risk than others. Greater awareness among young people is necessary to reduce the threat of infection among HCWs.


| INTRODUCTION
Pandemics have occurred throughout history and appear to be increasing in frequency, particularly because of the increasing emergence of viral zoonotic diseases. These are large-scale outbreaks of infectious diseases that can greatly increase morbidity and mortality worldwide and cause significant economic, social, and political disruption. 1 Furthermore, the impact on the health care system remains a great challenge, as recently demonstrated through the global spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which started in December 2019 in Wuhan, Hubei Province, China. 2 During the pandemic of coronavirus disease 2019  caused by SARS-CoV-2, health care workers (HCWs) were and are still on the frontlines battling the disease and are the most at risk of acquiring the infection as they are exposed to infected patients.
Previous experiences of a similar disease, severe acute respiratory syndrome (SARS), have left a distressing toll on care workers. 3 However, risk factors for SARS-CoV-2 infection among HCWs have not been well described, especially in African countries. 4 Currently, the COVID-19 pandemic continues its progression in Africa, which is determined largely by geography and the subsequent availability of resources. 5 Thus, it is imperative to ensure the safety of HCWs not only to safeguard continuous patient care but also to ensure that they do not transmit the virus. 6 The main issue in the care setting is to ward off and prevent the spread of COVID-19 to hospital staff. For the first month, the number of new daily COVID-19 cases was relatively low, but this number increased drastically after 42-46 days with an exponential trend and has certainly increased the risk of infection among HCWs in relation to worldwide pressure to produce enough barrier material (masks, hydroalcoholic gel, etc.) and personal protective equipment (PPE). Moreover, while the general population was advised to stay at home to adhere to social distancing rules, HCWs had to go to work in hospitals. Furthermore, the risk for infection may have been highest at the beginning when HCWs were not familiar with the use of PPE. 8 The World Health Organization (WHO) recommends the implementation of studies targeting HCWs assigned to care for patients with COVID-19, aiming to assess the risk of infection and transmission in this population. 9,10 Although many serological surveys have been performed in high-and middle-income countries assessing the risk for SARS-CoV-2 infection and seroconversion among frontline health care personnel, [11][12][13] few studies have been published in sub-Saharan countries. [14][15][16] The Pasteur Network in Africa conducted a multicentre prospective study entitled 'COVID-19 evaluation risk among health care workers in Africa' ('COVER-HCW'), based on one of the WHO's master protocols. 17 Such studies are crucial to inform decision-makers about better control strategies for HCWs in Africa and represent an opportunity to study infections in asymptomatic or paucisymptomatic persons.

Moreover, estimating infection rates and risk factors in this popula
Madagascar was among the countries that participated in the study during the first wave through the main hospitals that oversaw the first cases of COVID-19 in Antananarivo.
The aim of the present work was to assess SARS-CoV-2 risk infection among frontline COVID-19 HCWs during the first wave of SARS-CoV-2 in Antananarivo and explore risk factors for infection. paediatric departments. Nursing assistants, physiotherapists, stretcher bearers, radiologists and anaesthesiologists were also involved. As the number of cases increased, in addition to the workload, the other departments received also patients infected with COVID-19.

| Participants and data collection
During May 2020, all frontline staff were invited to participate in the cohort study on a voluntary basis. At the beginning of the study, in each hospital, after obtaining the director's agreement, all HCWs involved in the care of Covid-19 patients were gathered for an information session on the project.
At inclusion, participants were asked to complete a questionnaire with medical history, current symptoms and compliance with information on infection prevention and control measures. We also adminis-

| Statistical analysis
Descriptive statistical analysis was used to summarize the characteristics of HCWs; chi-square tests were performed for categorical variables and survival analysis to examine the relation between infection and HCW characteristics. For survival analysis, the duration of the follow-up time lasted from the date of inclusion until the date of positivity, either by RT-qPCR or by serology for those who became positive; it was rightcensored for those who did not present the event, and it ended at the date of last report for those who were not followed up until the end.
HCWs who had been positive at inclusion, either by RT-qPCR or serology, and those who did not have complete follow-up were excluded from the Cox model analysis. A backward stepwise selection variable (less than 0.20) was used in the univariate analyses to choose the final model in the multivariate analysis. All p values < 0.05 were considered statistically significant. All analyses were conducted with R software. 20 3 | RESULTS

| Characteristics of HCWs
The study lasted 7 months, with the start of inclusion on 7 May 2020 Regarding exposure to infected patients, 96 HCWs reported having been exposed to positive patients infected with SARS-CoV-2 who were cured and discharged, deceased, or other (transferred, etc.).
However, considering loss to follow-up during the survey period and  in HCWs aged younger than 30 years (Table 2).

| DISCUSSION
We conducted this cohort study to estimate the risk of SARS-CoV-2 infection and the associated factors among HCWs at the three main hospitals of Antananarivo who cared for COVID-19 patients. We Our study is among the few that have been performed in HCWs in sub-Saharan Africa, and the estimated seroprevalence reported here was higher than those found in urban Malawi, which observed a seroprevalence of 12.5%, 15 and was quite similar to the seroprevalence reported in the Democratic Republic of Congo at 41.2%. 14 These observed differences might be explained by differences in adherence to IPC measures, the use of PPE among HCWs, and other measures applied in the different settings (hand hygiene audits, availability of alcohol-based hand sanitizer, presence of surveillance system for nosocomial infections in patients). We also cannot exclude some differences due to methods, particularly serological tests. We found that the seropositivity in HCWs started to increase since the beginning of the study (May), reaching 31% in July, a trend that seems to parallel that of the epidemic in the general population until We found that the pandemic affected young HCWs more than others. The relative risk in HCWs aged younger than 30 years was five times higher than among older HCWs, even when adjusted for the number of contacts with severe disease leading to death. Young people might have behaviours that may lead them to be more at risk at work than others in the community (for example, less precautions taken outside work and during their occupational activities). This might also be explained by the measures adopted by the government, who authorized workers with comorbidities (high blood pressure, diabetes, etc.) to abstain from working or telecommuting; most of them were of advanced age and did not work during a certain period of the pandemic. In the study hospitals, those with concurrent conditions or older individuals who continued to work were asked by their supervi- or more frequent contact with the nursing staff and physicians during their hospital stay because they needed more meticulous care. The virus can be viable up to 1 month in severe patients versus generally less than 10 days in regular patients. [29][30][31] Our study had some limitations. Participation in our study was voluntary, and our sample of HCWs comprised those who were willing to take part in the study. This could have affected the incidence and risks found. It is possible that people who felt more at risk (older people, with comorbidities) would have participated.
However, we observed that the cohort was young, and only 32% had a comorbidity. Our limited sample size may also explain the absence of statistical significance observed for some of the factors listed by other studies to be potential risk factors for SARS-CoV-2 infection among HCWs.
We had difficulties in conducting surveys among HCWs, and only 36% of those invited consented to participate in the study. However, for those who agreed to participate, we observed good compliance with the study. The proportion of HCWs who participated at each follow-up was high and ranged from 84% to 94%, and 73% had a complete follow-up visit during the study. One limitation is that we were not able (and it's difficult to do so) to assess whether HCW contamination occurred in the community or at the hospital.

| CONCLUSION
Our study confirmed that HCWs on the front lines are at high risk of